With an increasing awareness of safety and security among people today, even in an elevator system, images taken by a security monitoring camera device (hereinafter also called monitoring camera device) mounted within the elevator car are commonly monitored and recorded in a building management/security office, or a security company. Furthermore, a simple security system is widely used which helps ensure the security, with the user privacy being protected, by displaying an image within the car for only several seconds on a display monitor (hereinafter also called monitor) installed in the elevator car or at an elevator hall.
When the camera device is connected to the monitor on which a camera image is displayed, a television signal (a signal based on a broadcast standard such as NTSC or PAL) is generally used in order to connect both units at lower cost. For that reason, before being output from the camera device, camera images captured by an image sensor are converted within the camera device into the television signal.
When the images are converted into the television signal, the number of pixels of the image sensor for the camera device differs in some situations from that of the television signal. To deal with this, image processing such as trimming and scaling up or down (enlargement or reduction) is implemented. In particular, when the pixel number of the television signal is greater than that of the camera image sensor, a non-image area (black image) is in some cases provided at or near the perimeter of the display screen.
In this case, however, a problem is that when the monitor for receiving the television signal to display a camera image thereon displays the non-image area (black image) as it is, provided at or near the perimeter of the screen for the television signal, the displayed image is unsightly and there can be no effective use of the monitor screen.
On the other hand, in a television system where received broadcast signals are displayed on the monitor, provision is generally made to allow the non-image area (black image) not to appear on the monitor by selecting a display mode. A method is proposed where when images having the non-image area in an upper and a lower portion thereof or the like are received, a boundary between the non-image area and the effective image area is detected to determine the display mode (refer to Japanese Unexamined Patent Publication No. H7-162751 (page 1, FIG. 1) and Japanese Unexamined Patent Publication No. 2006-229781 (page 1, FIG. 1)).
Conventionally, installation technicians for monitoring camera devices need to visually determine the boundary between an effective image area and a non-image area created resulting from the difference between the pixel number of the camera image sensor and that of the television signal, and then to manually make adjustments of an image display size and display position.
Also, in a system where images taken by the monitoring camera device are displayed, the use of techniques as disclosed in Japanese Unexamined Patent Publications Nos. H7-162751 and 2006-229781 enables a boundary to be automatically determined and then the display mode to be selected to the one that fits to the boundary. The system using the conventional techniques, however, makes determination when the lighting device for illuminating an area within a camera's field of vision is not turned on and the area therewithin is dark as well, thus resulting in the possibility for the display mode to be set to an inappropriate one. For instance, in a system where images taken by the monitoring camera device in an elevator car or cabin are displayed on a monitor (hereinafter called security camera-based monitoring system, or monitoring system), when the elevator system stays not operational for a predetermined period of time, the lighting device in the elevator car is in some cases turned off for economy of power. In this case, generally, only an emergency lamp with a small quantity of light for illuminating an elevator car control panel is switched on, with the area within the camera's field of vision being nearly pitch dark except for the neighborhood of the control panel illuminated by the lamp. In this situation, if boundary determination is made using the techniques in the previously mentioned Japanese Unexamined Patent Publications, and a display mode suitable to the boundary is selected, then the display mode is selected to display only the neighborhood of the elevator car control panel illuminated by the lamp. As a result, even when a passenger enters the elevator car after manipulation of a control panel in the hall, the monitor keeps displaying images with an inappropriate display mode being selected, as long as the display mode is not reset.